1. Field of the Invention
The present invention relates to a method and device for forming a pulley, and more particularly, to the method and device for forming a pulley of an electromagnetic clutch for a compressor, being able to be easily formed by a rolling process, which produces no chip, the pulley includes an inner hub having a bearing therein and being rotatably connected to a compressor etc., and includes an outer hub being disposed on the periphery of the inner hub with a predetermined gap in order to form an inserting space, into which a field core assembly composing an electromagnetic clutch is inserted, and being formed with a V-profile portion on the outer periphery thereof, and also the outer hub is formed in the same direction as the inner hub with respect to a friction surface.
2. Background of the Related Art
Generally, a pulley, which is used to an electromagnetic clutch for a compressor, is rotatably installed on a nose portion being projected from one side of a housing of the compressor, in a state of having a bearing, and transfers the power of a driving source (an engine or a driving motor) to a driving shaft of the compressor according to the discontinuous action of the electromagnetic clutch through a belt. The pulley includes an inner hub, an outer hub, a friction and a V-profile. The inner hub is rotatably connected to the nose portion of the housing in a state of having the bearing. The outer hub is disposed so that an annular space for receiving the field core assembly of the electromagnetic clutch is formed on the periphery of the inner hub. The friction surface connects the two ends of the inner hub and the outer hub so that a hub connected to the driving shaft of the compressor and a disk of a disk assembly are connected and disconnected according to the discontinuous action of the field core assembly. And, the V-profile is installed on the outer periphery of the outer hub in order to be covered with the belt connected to the driving source. That is, the inner hub and the outer hub are disposed in the same direction with respect to the friction surface, therefore, the annular space, which the field core assembly can be inserted therein, is formed between the inner hub and the outer hub.
As a conventional method to manufacture the above-described pulley, there are below two methods described in general. The first method is to perform turning operations using a lathe for a material formed by hot forging or by cold forging. And the second method is to press and to weld a sheave portion worked by the rolling of a rod and a hub portion worked to each other by turning operations of a cold forging material, and so on.
However, the first method is required to consider an allowance for turning operations. Therefore, the cost of the material is wasted, and lots of chips are produced after finishing the turning operations. Further, since there are different forging dies for each kind of a pulley, the turning operations by a manual loading should be required when first rough working. Therefore, the method cannot be achieved automatically and costs of the raw material cannot be saved.
Meanwhile, since the second method requires two individual materials to manufacture one pulley, the cost of the materials is increased and the rolling of the sheave is difficult. Therefore, it is difficult to manufacture a different type of pulley; and thereby, it cannot be expected to develop any new products.
To solve the above-described problems in the method for manufacturing pulleys, many methods and devices for forming a pulley have been recently developed, in which the pulley is manufactured with one material by rolling working, without any cutting. As a representative example, the method and device for forming a pulley is disclosed in the Korean Patent No. 271692.
According to the method and device in the prior art, the cap or the sheet base material is interposed between the rotating spindle and the fixed pin. Afterwards, different types of rollers press the rotating cap and the sheet base material which is rotating, therefore their thickness is decreased. Thereby, the cylindrical projections are formed on the periphery of the fixed pin, and the pulley in which the projections serve as a hub is manufactured.
However, in the prior art, when the pulley is manufactured by forming the cap, the process for forming the works in a cap type is required, and also the process for cutting ends of the formed cylindrical projections is required.
Furthermore, in the prior art, when the pulley is manufactured by forming the sheet material, the sheet material is inserted into the periphery of the pin, and then a press roller bends the edge portion of the sheet material. Afterwards, the sheet material is supported by means of a chuck, and then a cylindrical projection is formed. However, since there is a gap between the sheet material inserted into the periphery of the pin and a movable stop, the sheet works being underneath is movable. Therefore, when the edge portion of the sheet material is bent, the sheet material is slipped during rotation of a spindle. As well, since the press roller presses one side of the edge portion of the sheet material, the other side of the edge portion thereof is lifted. Therefore, the edge portion of the sheet material is not correctly bent; an intermediate hole of the sheet material for receiving the pin is also deformed. Thereby, the rate for producing an inferior product is high.
In the prior art, pulleys manufactured by variety of methods are disclosed. Among them, a pulley was manufactured by a method in that the inner hub and the outer hub are formed in the same direction with respect to the friction surface. However, how the inner hub and the outer hub which are formed in the same direction is not disclosed. In the prior art, the pulley, which composes specifically the electromagnetic clutch for the compressor, in which the inner hub and the outer hub are formed in the same direction with respect to the friction surface, and in which the inserting space for receiving the field core assembly of the electromagnetic clutch is formed between the inner hub and the outer hub, can not be manufactured. It can be known that only a pulley can be manufactured in which the inner hub and the outer hub are formed in opposite direction with respect to the friction surface.